A man impersonating a federal agent easily slipped past security at a major southern California airport, marking the latest of many embarrassing gaffes for the famously inept government agency charged with securing the nation’s transportation system.

The serious breach happened in San Diego and the scariest part is that the federal agency that got duped, the Transportation Security Administration (TSA), didn’t learn about it until local police discovered it weeks later. The phony U.S. Marshal presented fake law enforcement documents to enter secure areas of the airport with a woman he claimed was a prisoner, according to the local news report that broke the story.

After escorting his bogus prisoner to the gate and boarding her on a flight, the man simply walked out of San Diego International Airport, which annually serves millions of passengers, and returned home. Shortly after, he was arrested by local police and charged with kidnapping, false imprisonment and impersonating a peace officer.

The TSA was totally clueless about the breach until local law enforcement authorities notified it. Shocked agency officials claim they are investigating and “working with law enforcement and other departments to make sure this does not happen again.”

This sort of negligence seems to be par for the course at the scandal-plagued TSA, the 50,000-employee agency created after the 2001 terrorist attacks mainly to protect airlines. Although it has received hundreds of millions of dollars from Congress to fulfill its mission, the agency is best known for its mishaps and, in many cases, negligence.

Various Homeland Security Inspector General probes have determined that the TSA leaves airplanes vulnerable to terrorist attacks by failing to ensure the security of cargo packages and not adequately conducting background checks or training for agency workers who handle cargo. Dozens of other security failures have been documented over the years in other crucial areas nationwide, including TSA workers at three major airports missing hundreds of fake bombs during a covert exercise to determine if suspicious items could be smuggled into secure areas.

In the last few months alone, the TSA made headlines for giving security badges to a dozen illegal immigrants who had presented fake documents to work in sensitive areas of a busy U.S. airport and allowing a severely ill man with tuberculosis to board a 2,600-mile flight even though his name appeared on a Homeland Security “do-not-board” list.